The present invention relates to a jack stand and more particularly to a jack stand with a ratchet mechanism for controlling adjustment of the elevation of the saddle.
In the typical adjustable jack stand, there is a base that rests against the floor. A post extends out of and above the base and has a saddle on the exposed end. The load rests against the upper surface of the saddle. The elevation of the saddle can be changed by adjusting the length of the post that extends above the base. The desired elevation of the saddle, and of the load supported by the jack stand, is maintained typically in one of two ways.
In one embodiment, a plurality of holes are drilled through the post and spaced along the length thereof, and a pin is inserted through a hole in the post and a hole through the base to maintain the post at a predetermined elevation above the base. In another embodiment, a plurality of teeth formed on one edge of the post forms a ratchet that engages a pawl that is pivotally mounted on the base and attached to a lifting handle.
In the pin embodiment, it is typical for the pin to have a stay across both ends to prevent inadvertent withdrawal of the pin from the holes that would cause a sudden change in elevation and a commensurate shift in the load. However, this type of height adjustment mechanism also presents certain undesirable limitations. For example, removing one of the stays before removing the pin can be cumbersome, and mechanics tend to overlook replacing the stay or intentionally omitting the stay in order to avoid the inconvenience of dealing with the stay. Moreover, both the removed stay and the pin itself are easily misplaced in the work environment, rendering the jack stand inoperative until at least the pin is found. Additionally, it can be cumbersome to try to align the hole in the base with one of the holes in the post, and the weight of the post can cause it to slip out of alignment before the pin can be inserted through the aligned hole in the post. Such slippage can cause injury to the mechanic.
The ratchet and pawl mechanism does not require the mechanic to take any action to engage the pawl to the teeth on the post in the manner that holds the saddle at the desired elevation. However, the lifting handle can be moved in a manner that causes the pawl to disengage from the teeth on the post. It is possible that someone or something might inadvertently jostle the lifting handle while the jack stand is under load. If the pawl disengages from the post, then the saddle will undergo a sudden change of elevation that may cause the load to shift suddenly. Such sudden movements of the load can damage the load and/or the persons and property in the vicinity of the shifting load.
Moreover, there are a number of other ways for the pawl to be come disengaged from the tooth on the post. The pawl and the teeth on the post typically are cast iron that can break unexpectedly. The pivot pin that carries the pawl also can bend or break. When the height of the post is initially set by the operator of the jack stand, the pawl may not be properly engaged with a tooth, and operator may fail to check for or otherwise detect the improper engagement.
Thus, a need exists for an adjustable jack stand that overcomes these problems.
It is a principal object of the present invention to provide an improved adjustable jack stand.
It is another principal object of the present invention to provide an improved adjustable jack stand that offers an extra measure of safety in use.
It is a further principal object of the present invention to provide an improved adjustable jack stand that offers an extra measure of safety in use without unduly inconveniencing the mechanic.
It is a still further principal object of the present invention to provide an improved adjustable jack stand that offers an extra measure of safety in use without unduly inconveniencing the mechanic by combining a pin and hole height maintenance mechanism with a ratchet and pawl mechanism.
It is yet another principal object of the present invention to provide an improved adjustable jack stand that offers an extra measure of safety in use without unduly inconveniencing the mechanic by combining a ratchet and pawl height maintenance mechanism with a pin and hole mechanism wherein the holes in the post coordinate with the teeth in the post so that any engagement between the pawl and a tooth ensures that a pair of holes in the base and the post are aligned to receive a pin.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purpose of the invention, as embodied and broadly described herein, the adjustable jack stand of the present invention comprises a ratchet and pawl height adjustment mechanism and a pin and hole height adjustment mechanism that are coordinated with each other. More particularly, the adjustable jack stand comprises a body that defines a hollow interior and defines at least one foot member configured to rest against the surface of the floor. The jack stand body also defines a slide opening that permits access into the interior of the jack stand body.
The jack stand includes an elongated ratchet bar that defines a plurality of teeth disposed side-by-side along most of the length of a first portion of one elongated side edge of the ratchet bar. The first portion of the ratchet bar is slidably received within the slide opening of the jack stand body in a manner that orients the elongated ratchet bar with its axis of elongation parallel to the vertical direction when the foot member is resting on the floor surface. The ratchet bar also defines a plurality of holes disposed transversely therethrough and spaced at predetermined distances along the length of the ratchet bar. Each hole in the ratchet bar has an entrance and an exit disposed opposite the entrance. Desirably, the entrance and exit of each hole of the ratchet bar is recessed.
The jack stand includes a pawl that is pivotally connected to the jack stand body and configured and disposed for selectively engaging at least one of the teeth of the ratchet bar so as to prevent the ratchet bar from movement toward the foot member. A lifting handle is connected in communication with the pawl and is configured and disposed to be selectively positionable so as to release the pawl from engaging the teeth of the ratchet bar. Desirably, the lifting handle is non-rotatably connected to the pawl.
The jack stand includes a safety pin that is removably disposed within one of the plurality of holes of the ratchet bar. The pin is configured to be removably received within each of the plurality of holes of the ratchet bar. The pin is configured to be selectively positionable to protrude beyond each entrance and exit of each hole of the ratchet bar when removably received therein.
The jack stand body defines at least one pair of pin support sections. A first pin support section is disposed on one side of the slide opening, and a second pin support section is disposed on the opposite side of the slide opening and aligned with the first pin support section. Each pin support section is configured to receive and support the safety pin when the safety pin is positioned to protrude beyond each entrance and exit of each hole of the ratchet bar. The locations of the holes of the ratchet bar and the locations of the teeth of the ratchet bar are coordinated with one another and with the pawl in a particular spatial relationship so that any engagement between the pawl and one of the teeth of the ratchet bar ensures that one of the holes in the ratchet bar is aligned with the pair of pin support sections in the jack stand body.
Desirably, the pin defines a circular cylindrical shape, and each of the pin support sections likewise defines a corresponding semi-circular shape. An elongated tether is provided and has one section connected to the body and another section connected to the pin.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one embodiment of the invention and, together with the description, serve to explain the principles of the invention.